I think you can use nickel, copper and SS as filler materials. The following literature may help you.

Regards  

thx for your support

but I am interserted in fusion welding litrature

What type of fusion welding you are using? Here generally pre-heating or off-setting of welding torch is required for this process. If you go for resistance spot welding then also heat balance concept you have to use (i.e. smaller electrode dia is required in high conductive material side i.e Cu-Side and you can also use third material (Tunsten or Mo) in Cu side.)

I am talking about T\ig welding

I am interserted to increase strength on Cu side